Where do the voter names and addresses come from?

For “please vote” campaigns, all the voter information originates with state election authorities. They make voter rolls and histories available to the public in the interest of electoral system transparency. We typically purchase data from one of several third party companies that standardize it into a consistent format, making it easier for us to process. 

When we run voter registration campaigns, our data suppliers provide us with lists of voters who they believe are not registered to vote. In general, these lists are constructed by comparing other public and commercial data sources with the official voter rolls to identify people who are present on the former but not the latter.